In recent years, there is a constantly increasing demand for network capacity along with rapid development of high speed Internet, video services and large-capacity private-line services, thereby propelling development of networks toward larger capacity and higher rate. Operators worldwide have successively performed field test and started commercial network construction of high speed transmission systems. High speed transmission systems at as high as 40 Gbits/s now has become one of the focuses in the communication industry.
Currently, Optical Internetworking Forum (OIF) proposes an international standard for a line interface of communication system with a high speed optical link (typically at a bit rate of 40 Gbits/s), i.e., the SERDES Framer Interface Level 5 (SFI-5) standard. The SFI-5 standard is a protocol used between three primary components of such a high speed optical communication system at 40 Gbits/s including, i.e., a framer, a Forward Error Connection (FEC) processor and a Serializer/Deserializer (SERDES). For more details of SFI-5 standard, reference may be made to “SERDES Framer Interface Level 5 (SFI-5): Implementation Agreement for 40 Gbits/s Interface for Physical Layer Device” which is available from the OIF website at www.oiforum.com. As described in this document, an interface between respective components operates at a very high frequency due to a demand for huge throughout. Ideally, transmission of data over respective data channels (i.e., over respective optical fibers for transmission of the data) is mutually synchronous, that is, data is temporally aligned at the same instance of time. However, in practical application, different delays may arise in respective data channels due to noise and the like. For example, if data over a certain data channel is delayed, then data received over the respective channels will no longer be aligned. At this time, the data over the channel where a delay occurs is referred to as having been skewed. Therefore, a deskew process is required to compensate for differences between delays to align the data received, so that the data can be properly received.
In order to compensate for a delay, firstly skew detection and then deskew are required for each data channel. During skew detection, according to the SFI-5 standard, an important concept is data of a reference channel transmitted using a separate data path (i.e., another optical fiber), wherein one frame of data over the reference channel is aggregation of data slices of data at different instances of time over each data channel to be subject to skew detection, and a data slice over a certain data channel is compared with a data slice corresponding to the certain data channel over the reference channel to determine whether the data over the certain data channel has been skewed. Most of conventionally available solutions adopt a sequential skew detection method, also referred to as a serial matching method. In the serial matching method, a delay window is applied to data channels, and then data over the data channels is sequentially compared bit by bit with data over the reference channel corresponding to the data channels starting from the Most Significant Bit (MSB) to the Least Significant Bit (LSB), to search serially for a match between the respective data channels and the reference channel.
FIG. 1 is a schematic diagram illustrating a process of a conventionally typical serial matching method. In the serial solution illustrated in FIG. 1, bit-level comparison is performed between a data channel and a reference channel during data link transmission. According to the existing standard, consecutive 64-bit comparison is required to be performed for each data channel to be subject to skew detection, thereby resulting in an excessively long locking period. Due to noise and the like, mismatch frequently arises between a data channel and the reference channel in most cases, and at this time the data channel has to be unlocked, and according to the standard, there is one frame of time for waiting until the next matching operation, thereby resulting in waste of 64-bit time multiplied by the number of channels or more (bit time is also referred to as UI, where 1 UI is one-bit delay time). Moreover, noise is common in a high speed transmission environment, so that a mismatching point may arise over the link and consequently improper locking may occur, thereby wasting effective bandwidth. In order to overcome this situation, a signal with an excessively large skew has to be detected and compensated for. Therefore, larger bandwidth may be wasted due to limitation of the serial method in the case of a large number (e.g., 16) of data channels to be subject to skew detection. Additionally, the SFI-5 standard has defined the maximum allowable skew, which nevertheless may be difficult to be achieved due to serious influence of super high speed transmission of data via the interface, noise, etc.
In view of the foregoing circumstances, it is highly desired for a technology that can solve at least partly the foregoing problems present in the prior art.